﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace zy
{
    class Program
    {
        static void Main(string[] args)
        {
            const float a = 3.14f;
            Console.WriteLine("输入圆的半径:");
            int b = int.Parse(Console.ReadLine());
            Console.WriteLine(a*b*b);
            Console.ReadKey();
        }
    }
}
